Jenson Button posted the fastest time on the second day of Formula One’s opening four-day test at Jerez, but reliability and limited running remained the bigger story compared to times.

For what it was worth though, Button’s quickest time was nearly three seconds faster than the best posted by Kimi Raikkonen on Tuesday. Button clocked in at 1:24.165 after 43 laps of running in the McLaren MP4-29, compared to Raikkonen’s 1:27.104.

Raikkonen was second with a 1:24.812 after 47 laps aboard the Ferrari F14 T. Valtteri Bottas logged 35 in the Williams Fw36 at 1:25.344, with Nico Rosberg fourth at 1:25.588 in the new Mercedes.

Rosberg’s 97 laps Wednesday were four more than the combined total for the field on Tuesday.

Meanwhile Renault was left to go back to the drawing board after a frustrating day, with a suspected energy-storing issue.

Sebastian Vettel turned only eight laps in the RB10, with an unrepresentative fast time.

“We’ve not had a lot of running and have a few problems to sort out, but with such big rule changes it’s usual to have teething problems. That’s what tests are for, to sort those issues out,” said the four-time defending World Champion.

F1 rookie Marcus Ericsson’s day wasn’t much better as he posted only 11 laps in the new Caterham CT05.

Toro Rosso didn’t run at all, and Marussia failed to make it out of the garage with its yet-to-be-officially-unveiled MR03. Lotus, of course, isn’t at the test at all.

Some driver changes will occur for Thursday’s running, as teams continue to work through the development and niggling issues on their new cars.